Beam-column analysis is often referred to as a unique failure mode or even a buckling phenomena. This is not strictly true. It is a geometric non-linear stress analysis that computes an additional moment (and shear) caused by the combined effect of in-plane compression and lateral deflection.
For example, the figure below shows a beam under pressure P. The pressure induces an initial 'lateral' deflection δ. Next, axial load N is applied. Because the beam has already deflected, the axial load induces an additional applied moment equal to Nδ. This moment in turn induces even more lateral deflection δ' denoted by the dashed lines. The key is that if the axial load was applied by itself, zero lateral deflection would occur.
In HyperSizer, the initial lateral deflection that triggers beam-column behavior can be due to applied pressure, assumed initial imperfection, or applied end moments. The additional beam-column moments change the distribution cross-section stresses and therefore requires updated margin of safety checks.
The beam-column capability for panels is restricted to panels that can be treated as beams for pressure deflection calculation. Almost all stiffened panels and unstiffened panels that are long in the transverse direction fall into this category.
See the HME document for more detailed information.
